The present invention relates to intake manifold assemblies for reciprocating piston internal combustion engines and, in particular, to intake manifold assemblies fabricated from a polymeric material for internal combustion engines with positive crankcase ventilation.
Most automotive vehicles presently in production utilize an internal combustion reciprocating piston engine operating under an Otto cycle. The engine has an engine block with a plurality of cylindrical combustion chambers. A piston is slidably mounted within each combustion chamber. The piston is pivotally connected to a rod which is in turn pivotally connected to a crankshaft. To seal the combustion chamber each piston has an O-ring(s) fitted within an annular groove in a cylindrical side of the piston. During an intake stroke of the piston the crankshaft pulls the piston rod downward to induce a vacuum within the combustion chamber. The induced vacuum pumps a charge through an inlet valve into the combustion chamber. On a compression cycle, the inlet valve is closed and the piston is pushed upward by the piston rod providing a compression ratio typically exceeding 8:1. Upon ignition of the charge within the combustion chamber, the piston is pushed downward by the combustion energy. After combustion is virtually or totally complete, an exhaust valve opens and the crankshaft pushes the piston upwards to exhaust the charge and the cycle is then repeated.
During the compression and combustion cycles, very high gas pressure is experienced on the O-ring resulting in slight leakages of gas, often referred to as blow by. The blow by, which includes air, fuel, vapor and combustion byproducts, increases the pressure within the engine block which is exposed to the oil pan. If the blow by is not relieved, it will force the oil in the oil pan to escape via the dip stick and the engine will thus lose lubrication. To prevent the loss of lubrication, the blow by, prior to four decades ago was typically simply vented to the atmosphere.
In a genesis of emission control systems for automotive vehicles approximately 3-xc2xd decades ago, positive crankcase ventilation (PCV) was brought forth. PCV uses engine vacuum to draw fresh air through the crankcase. The fresh air enters through an air filter or through a separate PCV breather filter located in the interior of the air filter housing.
When the engine is running, intake manifold vacuum is applied to a PCV valve. The vacuum moves air through a hose into a rocker arm cover. From this location air flows through a cylinder head opening into the crankcase, where it mixes with the blow by. The mixture of blow by and induced air travels up through the cylinder head opening to the open PCV valve. Intake manifold vacuum moves the blow by and air mixture past the PCV valve into a hose connected with the intake manifold. The blow by and air mixture is then combined with the intake charge and enters the combustion chambers where they are burned.
In the most recent decade, there has been an increasing tendency to utilize polymeric, high-temperature, fiber-reinforced plastic intake manifolds for internal combustion engines. Polymeric manifolds have several advantages over prior tubular aluminum, cast aluminum or cast iron intake manifolds. The first advantage is that plastic manifolds do not require any significant machining, as did the prior aluminum or cast iron intake manifolds. Polymeric manifolds are lighter than their prior metallic counterparts and can be formed for production vehicles in a more accurate manner providing greater control of the flow path of incoming air and, as such, enhance the thermal dynamic efficiency of the engine.
In very cold climate conditions, there can be a freeze up in the connection of the PCV hose with the intake manifold. To alleviate possible conditions of freeze up, some PCV systems have a fitting that is heated by engine coolant at the point of intersection between the PCV hose and the manifold.
Many intake manifolds now also incorporate the air filter housing. Incorporation of the air filter housing lowers the overall cost of the two components. However, inclusion of the air filter housing causes the distance separating the PCV hose connection from the intake venturi of the intake manifold to be greater, resulting in two separate openings which can potentially freeze up in very cold weather.
It is desirable to provide an apparatus and method of utilization thereof for an intake manifold used with a PCV system having a relatively long passage between its intersection with the intake venturi and its intersection with the outer housing or boundary of the intake manifold.
To make manifest the above noted desire a revelation of the present invention is brought forth. In a preferred embodiment, the present invention provides a reciprocating piston internal combustion engine intake air manifold. The manifold has an intake venturi for throttled passage of filtered air into a plenum. The intake manifold has a positive crankcase ventilation passage having a first end intersecting with the venturi passage and a second end intersecting with an outer boundary of the manifold. A distance between the first and second ends of the positive crankcase ventilation passage is a major portion of a diameter of the venturi passage. A heat pipe is also provided adjacent a major portion of the ventilation passage. The heat pipe transfers thermal energy to the ventilation passage. The heat pipe prevents freeze up in the ventilation passage at the point of connection of the PCV hose and also at the point of the PCV passage intersection with the venturi passage. Additionally, the heat pipe aids in the prevention of freeze up of a throttle body positioned in the venturi passage. The heat pipe has a portion which is heated by contact with engine coolant.
It is an advantage of the present invention to provide a manifold having a PCV passage which is heated by a heat pipe. It is an advantage of the present invention to provide an internal combustion engine air intake manifold as above described which is fabricated from a polymeric material.
Other advantages of various embodiments of the present invention will become more apparent to those skilled in the art from the reading of the following detailed description and upon reference to the drawings.